With the cost of electricity being an important factor in operating lighting systems, especially on a large scale, there is a need to seek ways of reducing power consumption, to provide improved economy. This is especially true of the fluorescent lighting configurations found in large office blocks and other industrial premises.
It has been found possible to reduce the voltage supply to lights without producing a noticeable drop in light output and it has been proposed to achieve this by means of a transformer in order to give a power reduction to the system. With fluorescent lamps, in order to ensure reliable ignition upon switching on, it is however necessary to provide the full rated mains voltage at the time of switch on. To achieve this, it would in theory be possible to provide a transformed output during normal running of the lamps, but at start up, the transformer would be switched out and full mains voltage directly applied to the lamps. A major problem with such a configuration, especially with banks of lamps, is the power surge that is generated. A 10 kva transformer for a bank of up to 200 lamps when switched, could generate a surge of the order of 400 amps, which among other things would rapidly degrade the switching contacts employed and be unreliable in use.